We seek to determine whether the nerve growth factor (NGF) produced by the submaxillary gland of mouse is an important source of NGF for maintenance of the peripheral nervous system or whether other sources are of primary importance. If the latter is true, we propose to locate the important extra-submaxillary glandular sources and purify and characterize the NGF from these sources to determine whether NGF exists as 7S NGF or as some other molecular form. We also propose to characterize the NGF-like activity of C6 glioma cells to determine whether it may actually be a factor other than NGF and to screen a large number of tissue culture cell lines to determine which types of cells may secrete NGF. If a cell line is found which secretes sufficient amounts of NGF, the NGF will be purified and characterized.